Field of the Invention
The invention relates to a chair, in particular an office chair, having a backrest that is articulated on a seat that can be moved synchronously with the backrest. A sliding guide connects the front region of the seat to a seat carrier and a seat link connects the rear region of the seat to the seat carrier.
Seating furniture and, in particular, chairs in which the seat surface and the backrest move synchronously are used with various synchronizing mechanisms. The synchronizing mechanism serves to change the position of the seat surface at the same time as the backrest is adjusted.
A chair in which the inclination of the backrest and the seat is synchronously adjustable is known from published German Patent Application DE 42 19 599 A1. In the case of this chair, as the inclination of the backrest increases, the seat surface is raised by a seat link that is articulated on the rear region of the seat surface and on the seat carrier. The seat surface is drawn in the rearward direction at the same time by a drag lever that is connected rotatably to the seat surface and to the backrest link. Because of this raising action of the seat surface in the rear region, which is directed toward the backrest, the user may slide forward on the seat surface as the backrest leans back.
With a synchronous movement of the backrest and seat surface, however, the seat surface should be inclined in the rearward and downward directions at least to the extent where the pushing force exerted by the user as he/she leans back on the seat or the seat surface is absorbed.
It is accordingly an object of the invention to provide a chair which overcomes the above-mentioned disadvantageous of the prior art apparatus of this general type. More specifically, it is an object of the invention to provide a chair, in particular an office chair, with a particularly suitable synchronizing mechanism that can be realized in a straightforward manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, a chair, in particular, an office chair that includes: a seat carrier; a backrest; a backrest carrier articulating the backrest on the seat carrier; and a seat having a front region, a rear region, and a seat surface that is defined by the front region and the rear region. The seat surface is configured for moving synchronously with the backrest. The chair also includes a first sliding guide connecting the front region to the seat carrier; a seat link connecting the rear region to the seat carrier; a second sliding guide located in the backrest carrier for synchronizing a movement of the backrest and a movement of the seat surface; a top connection that connects the seat link to the seat and that defines a top point of rotation; and a bottom connection that connects the seat link to the seat carrier and that defines a bottom point of rotation. The top point of rotation is located to define a distance that is between the top point of rotation and the backrest. The bottom point of rotation is located to define a distance that is between the bottom point of rotation and the backrest. The distance that is between the top point of rotation and the backrest is smaller than the distance that is between the bottom point of rotation and the backrest.
In accordance with an added feature of the invention, the top connection includes a slot that guides the top point of rotation, and the slot is formed in the backrest carrier.
In accordance with an additional feature of the invention, the first sliding guide is located in the front region of the seat and the first sliding guide runs obliquely downward toward the seat carrier.
In accordance with a further feature of the invention, the seat link is curved concavely towards the seat.
In accordance with a further added feature of the invention, the seat link has a concave surface located opposite the seat.
In accordance with a further additional feature of the invention, there is provided, a connection that connects the backrest carrier to the seat carrier and that defines an additional point of rotation. The backrest has a rearwardly inclined position in which the top point of rotation is located at a lower level in relation to the seat surface than the additional point of rotation.
On the one hand, the distance between the top point of rotation, which connects the seat link to the seat surface, and the backrest is smaller than the distance between the bottom point of rotation, which connects the seat link to the seat carrier, and the backrest. Thus, as the inclination of the backrest increases, the seat surface, rather than being raised, is advantageously lowered. On the other hand, a sliding guide for the seat surface is provided in the backrest link for synchronization between the movement of the backrest and the movement of the seat surface.
The invention is based here on the consideration that, in the case of a chair or piece of seating furniture with an adjustable seat surface and an adjustable backrest, the possible adjustments of the seat surface, on the one hand, and backrest, on the other hand, may first of all be regarded independently of one another. The design thus initially has two degrees of freedom. The possible adjustment of the backrest here has just a single degree of freedom if the backrest is articulated on the seat carrier in a straightforward manner via the backrest carrier, which is connected rigidly to the backrest and is fastened rotatably on the seat carrier via a single rotary spindle. Furthermore, the seat surface may have more complex possible adjustments, although, in a manner analogous to the adjustability of the backrest, it may be assumed that it is also possible to describe the possible adjustments of the seat surface with a single degree of freedom. The movement of the seat surface here may be both a translation and a tilting movement or a combination of different types of movement.
Coupling the movements of the seat surface, on the one hand, and of the backrest, on the other hand, should first of all ensure that each possible position of the backrest is assigned a position of the seat surface, as a result of which the entire design is limited to one degree of freedom. These requirements and a coupling mechanism that has a permanently stable and a straightforward design, are fulfilled by providing a sliding guide for the seat surface in the backrest link. A particularly straightforward synchronizing mechanism is thus provided overall.
For this purpose, the seat surface may be guided in a slot, provided in the backrest link, via a rigid spindle which is connected to the seat surface. Advantageously, however, the top point of rotation, which is common to the seat surface and the seat link, is guided in a corresponding slot in the backrest link. It is expedient here for the seat link to be configured such that it is curved concavely in the direction of the seat surface.
The sliding guide provided in the front seat region may be realized by a slot provided in the seat carrier and a spindle which is connected rigidly to the seat surface, or by a cylinder. Irrespective of this, a sliding guide which runs obliquely downward in the direction of the seat carrier is advantageously provided. By virtue of the inclined arrangement of the front sliding guide of the seat surface, the sliding guide acting as length-compensation element, undesired raising of the front edge of the seat surface as the backrest is inclined back is avoided, and in addition, the front edge of the seat surface is lowered as the backrest is inclined back. This lowering action becomes more pronounced, the more the inclination of the sliding guide deviates from the horizontal and runs in the direction of the vertical.
From the point of view of ergonomics, the comfort is increased by the forward and downward inclination of the seat link, starting from the top point of rotation, which is connected to the seat surface, of the seat link. As the backrest is inclined back, the seat surface is lowered predominantly in its rear region, while, at the same time, the front edge of the seat surface moves in the rearward and downward directions. As a result, the seat surface achieves, as desired, a greater freedom of movement in its rear region than in its front region.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in chair, in particular office chair, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.